U.S. patent application number 15/317856 was filed with the patent office on 2017-05-18 for photoelectric conversion element, and image sensor, solar cell, single color detection sensor and flexible sensor each of which uses said photoelectric conversion element.
This patent application is currently assigned to TORAY INDUSTRIES, INC.. The applicant listed for this patent is TORAY INDUSTRIES, INC.. Invention is credited to Jinwoo KWON, Tsuyoshi TOMINAGA, Masaaki UMEHARA.
Application Number | 20170141320 15/317856 |
Document ID | / |
Family ID | 55350621 |
Filed Date | 2017-05-18 |
United States Patent
Application |
20170141320 |
Kind Code |
A1 |
UMEHARA; Masaaki ; et
al. |
May 18, 2017 |
PHOTOELECTRIC CONVERSION ELEMENT, AND IMAGE SENSOR, SOLAR CELL,
SINGLE COLOR DETECTION SENSOR AND FLEXIBLE SENSOR EACH OF WHICH
USES SAID PHOTOELECTRIC CONVERSION ELEMENT
Abstract
The present invention has the configuration described below for
the purpose of providing a photoelectric conversion efficiency
element which exhibits high charge mobility, while having high
photoelectric conversion efficiency. A photoelectric conversion
element which comprises at least one organic layer between a first
electrode and a second electrode, and which is characterized in
that the organic layer contains a first compound represented by
general formula (1) and a second compound that has a maximum value
of absorption coefficient of 5.times.10.sup.4 cm.sup.-1 or more at
a wavelength of 400-700 nm.
Inventors: |
UMEHARA; Masaaki; (Otsu-shi,
Shiga, JP) ; TOMINAGA; Tsuyoshi; (Seoul, KR) ;
KWON; Jinwoo; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TORAY INDUSTRIES, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
TORAY INDUSTRIES, INC.
Tokyo
JP
|
Family ID: |
55350621 |
Appl. No.: |
15/317856 |
Filed: |
August 5, 2015 |
PCT Filed: |
August 5, 2015 |
PCT NO: |
PCT/JP2015/072229 |
371 Date: |
December 9, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/301 20130101;
C07D 307/79 20130101; H01L 51/0037 20130101; H01L 51/0053 20130101;
H01L 51/0068 20130101; H01L 27/307 20130101; C07C 15/38 20130101;
H01L 51/4253 20130101; H01L 51/0035 20130101; H01L 51/0054
20130101; C07C 2603/52 20170501; H01L 51/0058 20130101; H01L 51/424
20130101; Y02E 10/549 20130101; H01L 51/0055 20130101; H01L 51/0073
20130101; C07C 2603/44 20170501 |
International
Class: |
H01L 51/00 20060101
H01L051/00; C07D 307/79 20060101 C07D307/79; C07C 15/38 20060101
C07C015/38; H01L 51/42 20060101 H01L051/42; H01L 27/30 20060101
H01L027/30 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2014 |
JP |
2014-167325 |
Claims
1. A photoelectric conversion element including a first electrode,
a second electrode, and at least one organic layer existing
therebetween, the organic layer containing a first compound, and a
second compound in which the maximum value of an absorption
coefficient at a wavelength of 400 to 700 nm is 5.times.10.sup.4
cm.sup.-1 or more, the first compound being represented by the
following general formula (1): ##STR00053## (in the general formula
(1), R.sup.1 to R.sup.12 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, a carbonyl
group, a carboxyl group, an oxycarbonyl group, a carbamoyl group,
an amino group, a nitro group, a cyano group, a silyl group and
--P(.dbd.O)R.sup.13R.sup.14; R.sup.13 .sub.and R.sup.14 each
represent an aryl group or a heteroaryl group; adjacent
substituents may be linked together to form a ring structure; and
R.sup.5 and R.sup.12 in the general formula (1) each represent a
group represented by the following general formula (2) or (3):
##STR00054## (in the general formula (2) or (3), R.sup.15 to
R.sup.24 may be the same or different, and each represent a group
selected from the group consisting of hydrogen, an alkyl group, a
cycloalkyl group, a heterocyclic group, an alkenyl group, a
cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio
group, an aryl ether group, an aryl thioether group, an aryl group,
a heteroaryl group, a halogen, a carbonyl group, a carboxyl group,
an oxycarbonyl group, a carbamoyl group, an amino group, a nitro
group, a cyano group, a silyl group and
--P(.dbd.O)R.sup.13R.sup.14; R.sup.13 and R.sup.14 each represent
an aryl group or a heteroaryl group; R.sup.16 to R.sup.19 and
R.sup.21 to R.sup.24 may form a ring between adjacent substituents;
X represents an oxygen atom, a sulfur atom or --NR.sup.25; and
R.sup.25 is hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an aryl group or a heteroaryl group)).
2. The photoelectric conversion element according to claim 1,
wherein R.sup.5 and R.sup.12 in the general formula (1) are each
represented by the general formula (2), and R.sup.15 in the general
formula (2) represents an alkyl group, an alkoxy group, an aryl
group or a heteroaryl group.
3. The photoelectric conversion element according to claim 1,
wherein R.sup.5 and R.sup.12 in the general formula (1) are each
represented by the general formula (3), and R.sup.29 in the general
formula (3) represents an alkyl group, an alkoxy group, an aryl
group or a heteroaryl group.
4. The photoelectric conversion element according to claim 1,
wherein R.sup.5 and R.sup.12 in the general formula (1) are each
represented by the general formula (3), and X in the general
formula (3) represents an oxygen atom.
5. The photoelectric conversion element according to claim 1,
wherein the second compound is a derivative selected from a
thiophene derivative, a pyrene derivative and a perylene
derivative.
6. The photoelectric conversion element according to claim 5,
wherein the second compound is a compound represented by the
following general formula (4): ##STR00055## (in the general formula
(4), R.sup.25 to R.sup.28 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, an amino
group, a silyl group, --P(.dbd.O)R.sup.29R.sup.30, and a group
represented by the following general formula (5); R.sup.29 and
R.sup.30 each represent an aryl group or a heteroaryl group; m
represents an integer of 1 to 6; and at least one of R.sup.25 to
R.sup.28 represents a group represented by the following general
formula (5). [Chemical Formula 4] -L CN).sub.n (5) (in the general
formula (5), n represents 1 or 2; L represents an alkenediyl group,
an arylenediyl group or a heteroarylenediyl group when n represents
1; and L represents an aklenetriyl group, an arylenetriyl group or
a heteroarylenetriyl group when n represents 2)).
7. The photoelectric conversion element according to claim 5,
wherein the second compound is a compound represented by the
following general formula (6): ##STR00056## (in the general formula
(6), R.sup.31 to R.sup.34 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, an amino
group, a silyl group, --P(.dbd.O)R.sup.35R.sup.36, and a group
represented by the following general formula (5); R.sup.35 and
R.sup.36 each represent an aryl group or a heteroaryl group; and at
least one of R.sup.31 to R.sup.34 represents a group represented by
the following general formula (5): [Chemical Formula 6] -L
CN).sub.n (5) (in the general formula (5), n represents 1 or 2; L
represents an alkenediyl group, an arylenediyl group or a
heteroarylenediyl group when n represents 1; and L represents an
aklenetriyl group, an arylenetriyl group or a heteroarylenetriyl
group when n represents 2)).
8. The photoelectric conversion element according to claim 5,
wherein the second compound is a compound represented by the
general formula (7): ##STR00057## (in the general formula (7),
R.sup.37 to R.sup.38 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, an amino
group, a cyano group, a silyl group and
--P(.dbd.O)R.sup.39R.sup.40; and R.sup.39 and R.sup.40 each
represent an aryl group or a heteroaryl group).
9. The photoelectric conversion element according to claim 1,
wherein the organic layer includes a photoelectric conversion
layer, and the photoelectric conversion layer contains the first
compound and the second compound.
10. The photoelectric conversion element according to claim 1,
wherein the first compound is a p-type semiconductor material, and
the second compound is a n-type semiconductor material.
11. The photoelectric conversion element according to claim 1,
wherein the first compound and the second compound each have a
charge mobility of 1.times.10.sup.-9 cm.sup.2/Vs or more.
12. The photoelectric conversion element according to claim 1,
wherein the organic layer has a thickness of 20 nm or more and 200
nm or less.
13. An image sensor comprising the photoelectric conversion element
according to claim 1.
14. The image sensor according to claim 13, including two or more
photoelectric conversion elements, at least one of the
photoelectric conversion elements being the photoelectric
conversion element according to any one of claims 1 to 12.
15. The image sensor according to claim 14, wherein the two or more
photoelectric conversion elements have a laminated structure.
16. A solar cell comprising the photoelectric conversion element
according to claim 1.
17. A single color detection sensor comprising the photoelectric
conversion element according to claim 1.
18. A flexible sensor comprising the photoelectric conversion
element according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a photoelectric conversion
element which can convert light into electric energy. More
particularly, the present invention relates to a photoelectric
conversion element which can be employed in the fields of solar
cells, image sensors, and the like.
BACKGROUND ART
[0002] The photoelectric conversion element capable of converting
light into electric energy can be employed in solar cells, image
sensors, and the like. In particular, there has widely been used an
image sensor in which a current generated by incident light in a
photoelectric conversion element is read out by CCD and CMOS
circuits.
[0003] In an image sensor using a photoelectric conversion element,
an inorganic substance has hitherto been employed as a material
composing the photoelectric conversion film. However, since the
inorganic substance has low selectivity of color (absorption of
specific colors), it has been necessary that light of each of
colors (red, green and blue) in incident light be selectively
transmitted, and absorbed in a photoelectric conversion film.
However, during imaging a fine object, use of the color filter may
lead to an interference between the pitch of the object and that of
an image element, thus generating an image which is different from
an original image (Moire defects). For suppressing the defects, an
optical lens etc. is needed, but there is a disadvantage that a
color filter and an optical lens reduce efficiency for light
utilization and an aperture ratio.
[0004] Meanwhile, growing demands for higher resolution of the
image sensor create an opportunity of the progress of
microfabrication of pixels. Accordingly, the size of pixels further
decreases, and reduction in size of pixels leads to a decrease in
quantity of light which reaches the photoelectric conversion
element of each pixel, thus causing deterioration of
sensitivity.
[0005] To solve these problems, a study has been made of a
photoelectric conversion element using an organic compound. Since
the organic compound can selectively absorb light in a specific
wavelength region of light being incident according to a molecular
structure, no color filter is required. Further, since the organic
compound has a large absorption coefficient, efficiency for light
utilization can be improved. There have been known, as a
photoelectric conversion element using the organic compound,
specifically, element structures in which a p-n junction structure
and a bulk heterojunction structure are introduced into a
photoelectric conversion film sandwiched between an anode and a
cathode. For example, Patent Document 1 discloses an organic
photoelectric material containing a compound having a
thiophene-containing aromatic group in which an aromatic ring is
fused.
PRIOR ART DOCUMENTS
Patent Documents
[0006] Patent Document 1: Japanese Patent Laid-open Publication No.
2014-17484
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] Although superiority of use of the photoelectric conversion
element using an organic compound particularly in an image sensor
can be confirmed, in principle, there are numerous technical
problems for putting it into practical use.
[0008] For example, in Patent Document 1, a thiophene-based
compound having a large absorption coefficient (hereinafter,
referred to as a compound of Patent Document 1) is used. A
photoelectric conversion element using the compound of Patent
Document 1 exhibits relatively high photoelectric conversion
efficiency, but further improvement of photoelectric conversion
efficiency has been required.
[0009] Meanwhile, as organic compounds to be used in the
photoelectric conversion element, many compounds having a large
absorption coefficient (hereinafter, referred to as other
light-absorbing compounds) are known in addition to the compound of
Patent Document 1. However, with photoelectric conversion elements
using these other light-absorbing compounds, sufficient
photoelectric conversion efficiency is not obtained, and
improvement of photoelectric conversion efficiency has been
required.
[0010] Thus, an object of the present invention is to solve the
problems of the prior art and to provide a photoelectric conversion
element having higher photoelectric conversion efficiency.
Solutions to the Problems
[0011] The inventors of the present application gave attention to
the charge mobility of a photoelectric conversion element for
solving the above-mentioned problems. Specifically, the reason why
a photoelectric conversion element using the compound of Patent
Document 1 exhibited relatively high photoelectric conversion
efficiency, whereas photoelectric conversion elements using the
other light-absorbing compounds did not exhibit sufficient
photoelectric conversion efficiency was thought to be that the
compound of Patent Document 1 had sufficient charge mobility,
whereas the other light-absorbing compounds did not have sufficient
charge mobility. Thus, the inventors of the present application
tried to improve the charge mobility of the other light-absorbing
compounds, but it was difficult to design and synthesize a molecule
that improves charge mobility while maintaining a large absorption
coefficient. Thus, the inventors of the present application
conceived improvement of the photoelectric conversion efficiency of
photoelectric conversion elements using the other light-absorbing
compounds by combining the other light-absorbing compounds with a
compound having sufficient charge mobility.
[0012] First, the inventors of the present application examined
naphthacene as a compound having charge mobility. However, even
when naphthacene was combined with the other light-absorbing
compounds, high photoelectric conversion efficiency was not
obtained. Thus, the inventors of the present application have
further conducted studies repeatedly, and found that high
photoelectric conversion efficiency is obtained by combining the
other light-absorbing compounds with a fused ring aromatic compound
having a specific structure. The present invention is as
follows.
[0013] The present invention is directed to a photoelectric
conversion element including a first electrode, a second electrode,
and at least one organic layer existing therebetween, the organic
layer containing a first compound, and a second compound in which
the maximum value of an absorption coefficient at a wavelength of
400 to 700 nm is 5.times.10.sup.4 cm.sup.-1 or more, the first
compound being represented by the following general formula
(1):
##STR00001##
(in the general formula (1), R.sup.1 to R.sup.12 may be the same or
different, and each represent a group selected from the group
consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14; R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group;
adjacent substituents may be linked together to form a ring
structure; and
[0014] R.sup.5 and R.sup.12 in the general formula (1) each
represent a group represented by the following general formula (2)
or (3):
##STR00002##
(in the general formula (2) or (3), R.sup.15 to R.sup.24 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14; R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group;
R.sup.15 to R.sup.19 and R.sup.21 to R.sup.24 may form a ring
between adjacent substituents; X represents an oxygen atom, a
sulfur atom or --NR.sup.25; and R.sup.25 is hydrogen, an alkyl
group, a cycloalkyl group, a heterocyclic group, an aryl group or a
heteroaryl group)).
Effect of the Invention
[0015] According to the present invention, it is possible to
provide a photoelectric conversion element having high
photoelectric conversion efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic sectional view showing an example of a
photoelectric conversion element of the present invention.
[0017] FIG. 2 is a schematic sectional view showing an example of a
photoelectric conversion element of the present invention.
[0018] FIG. 3 is a schematic sectional view showing an example of a
photoelectric conversion element of the present invention.
[0019] FIG. 4 is a schematic sectional view showing an example of a
photoelectric conversion element of the present invention.
[0020] FIG. 5 is a schematic sectional view showing an example of a
laminated structure of a photoelectric conversion element in an
image sensor of the present invention.
[0021] FIG. 6 is a schematic sectional view showing an example of a
laminated structure of a photoelectric conversion element in an
image sensor of the present invention.
EMBODIMENT OF THE INVENTION
[0022] <Photoelectric Conversion Element>
[0023] A photoelectric conversion element of the present invention
includes a first electrode, a second electrode, and at least one
organic layer existing therebetween, the organic layer containing a
first compound, and a second compound in which the maximum value of
an absorption coefficient at a wavelength of 400 to 700 nm is
5.times.10.sup.4 cm.sup.-1 or more, the first compound being
represented by the following general formula (1).
##STR00003##
[0024] In the general formula (1), R.sup.1 to R.sup.12 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14. R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group.
Adjacent substituents may be linked together to form a ring
structure.
[0025] R.sup.5 and R.sup.12 in the general formula (1) each
represent a group represented by the following general formula (2)
or (3).
##STR00004##
In the general formula (2) or (3), R.sup.15 to R.sup.24 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14. R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group.
R.sup.16 to R.sup.19 .sub.and R.sup.21 to R.sup.24 may form a ring
between adjacent substituents. X represents an oxygen atom, a
sulfur atom or --NR.sup.25. R.sup.25 is hydrogen, an alkyl group, a
cycloalkyl group, a heterocyclic group, an aryl group or a
heteroaryl group.
[0026] Hereinafter, the "first compound represented by the general
formula (1)" may be referred to as a "first compound". In the
present invention, the "second compound in which the maximum value
of an absorption coefficient at a wavelength of 400 to 700 nm is
5.times.10.sup.4 cm.sup.-1 or more" may be referred to as a "second
compound" hereinafter.
[0027] Examples of the photoelectric conversion element of the
present invention are shown in FIGS. 1 to 4.
[0028] FIG. 1 shows an example of a photoelectric conversion
element including a first electrode 10, a second electrode 20, and
one organic layer 11 interposed therebetween. The organic layer 11
in FIG. 1 is a photoelectric conversion element 15 which converts
light into electric energy. The organic layer in the present
invention is a layer containing an organic compound, and examples
of the organic layer include photoelectric conversion layers and
charge blocking layers.
[0029] A description will be made below for FIGS. 2 to 4 by
enumerating, as an example, the case where the first electrode 10
is an cathode and the second electrode 20 is an anode. As shown in
FIGS. 2 to 4, a charge blocking layer may be inserted, in addition
to a photoelectric conversion layer, between the cathode and the
anode. The charge blocking layer is a layer that serves to block
electrons or holes. The charge blocking layer serves as an electron
blocking layer 13 when inserted between the cathode and the
photoelectric conversion layer, and serves as a hole blocking layer
17 when inserted between the anode and the photoelectric conversion
layer 15. The photoelectric conversion element may include only one
of these charge blocking layers (FIGS. 2 and 3), or both of these
charge blocking layers (FIG. 4).
[0030] Further, when the photoelectric conversion layer is composed
of two or more photoelectric conversion materials, the
photoelectric conversion layer may be a single layer in which two
or more photoelectric conversion materials are mixed, or a
plurality of layers in which layers composed of one or more
photoelectric conversion material(s) are laminated. Furthermore,
the photoelectric conversion layer may have a structure in which a
mixed layer is mixed with each single layer.
[0031] (First Compound)
[0032] The first compound represented by the general formula (1) in
the present invention will be described.
##STR00005##
[0033] In the general formula (1), R.sup.1 to R.sup.12 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14. R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group.
Adjacent substituents may be linked together to form a ring
structure.
[0034] In the present invention, hydrogen may include
deuterium.
[0035] The alkyl group represents, for example, a saturated
aliphatic hydrocarbon group such as a methyl group, an ethyl group,
an n-propyl group, an isopropyl group, an n-butyl group, a
sec-butyl group, or a tert-butyl group, and optionally has a
substituent. There is no particular limitation on additional
substituent when the alkyl group is substituted, and examples
thereof include an alkyl group, an aryl group, a heteroaryl group,
and the like. This aspect is common for the additional substituent
when each substituent such as a cycloalkyl group or a heterocyclic
group as described below is substituted. There is no particular
limitation on the carbon number of the alkyl group, and the carbon
number is usually in a range of 1 or more and 20 or less, and more
preferably 1 or more and 8 or less, in view of availability and
costs. When the alkyl group is substituted, the carbon number of
the alkyl group includes the carbon number of the additional
substituent. When each substituent such as a cycloalkyl group or a
heterocyclic group as described below is substituted, the carbon
number of each substituent includes the carbon number of the
additional substituent.
[0036] The cycloalkyl group represents, for example, a saturated
alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl,
norbornyl, or adamantyl, and optionally has a substituent. There is
no particular limitation on the carbon number of the alkyl group
moiety, and the carbon number is usually in a range of 3 or more
and 20 or less.
[0037] The heterocyclic group represents, for example, an aliphatic
ring having an atom other than carbon, such as a pyran ring, a
piperidine ring or a cyclic amide, and optionally has a
substituent. There is no particular limitation on the carbon number
of the heterocyclic group, and the carbon number is usually in a
range of 2 or more and 20 or less.
[0038] The alkenyl group represents, for example, an unsaturated
aliphatic hydrocarbon group having a double bond, such as a vinyl
group, an allyl group, or a butadienyl group, and optionally has a
substituent. There is no particular limitation on the carbon number
of the alkenyl group, and the carbon number is usually in a range
of 2 or more and 20 or less.
[0039] The cycloalkenyl group represents, for example, an
unsaturated aliphatic hydrocarbon group having a double bond, such
as a cyclopentenyl group, a cyclopentadienyl group or a
cyclohexenyl group, and optionally has a substituent. There is no
particular limitation on the carbon number of the cycloalkenyl
group, and the carbon number is usually in a range of 2 or more and
20 or less.
[0040] The alkynyl group represents, for example, an unsaturated
aliphatic hydrocarbon group having a triple bond, such as an
ethynyl group, and optionally has a substituent. There is no
particular limitation on the carbon number of the alkynyl group,
and the carbon number is usually in a range of 2 or more and 20 or
less.
[0041] The alkoxy group represents, for example, a functional group
in which aliphatic hydrocarbon groups are bonded through an ether
bond, such as a methoxy group, an ethoxy group, or a propoxy group,
and this aliphatic hydrocarbon group optionally has a substituent.
There is no particular limitation on the carbon number of the
alkoxy group, and the carbon number is usually in a range of 1 or
more and 20 or less.
[0042] The alkylthio group is a group in which the oxygen atom of
the ether bond in the alkoxy group is replaced by a sulfur atom.
The hydrocarbon group in the alkylthio group optionally has a
substituent. There is no particular limitation on the carbon number
of the alkylthio group, and the carbon number is usually in a range
of 1 or more and 20 or less.
[0043] The aryl ether group represents, for example, a functional
group in which aromatic hydrocarbon groups are bonded through an
ether bond, such as a phenoxy group, and the aromatic hydrocarbon
group optionally has a substituent. There is no particular
limitation on the carbon number of the aryl ether group, and the
carbon number is usually in a range of 6 or more and 40 or
less.
[0044] The aryl thioether group is a group in which the oxygen atom
of the ether bond in the aryl ether group is replaced by a sulfur
atom. The aromatic hydrocarbon group in the aryl ether group
optionally has a substituent. There is no particular limitation on
the carbon number of the aryl ether group, and the carbon number is
usually in a range of 6 or more and 40 or less.
[0045] The aryl group represents, for example, an aromatic
hydrocarbon group such as a phenyl group, a naphthyl group, a
biphenyl group, a fluorenyl group, a phenanthryl group, a
triphenylenyl group, or a terphenyl group. The aryl group
optionally has a substituent. There is no particular limitation on
the carbon number of the aryl group, and the carbon number is
usually in a range of 6 or more and 40 or less.
[0046] The heteroaryl group represents a cyclic aromatic group
having one or plural atom (s) other than carbon in the ring, such
as a furanyl group, a thiophenyl group, a pyridyl group, a
quinolinyl group, a pyrazinyl group, a pyrimidinyl group, a
triazinyl group, a naphthylidyl group, a benzofuranyl group, a
benzothiophenyl group, or an indolyl group, and the heteroaryl
group optionally has a substituent. There is no particular
limitation on the carbon number of the heteroaryl group, and the
carbon number is usually in a range of 2 or more and 30 or
less.
[0047] The halogen represents fluorine, chlorine, bromine, or
iodine.
[0048] The amino group optionally has a substituent. Examples of
the substituent include an aryl group and a heteroaryl group, and
these substituents may be further substituted.
[0049] The silyl group represents, for example, a functional group
having a bond to a silicon atom, such as a trimethylsilyl group,
and optionally has a substituent. There is no particular limitation
on the carbon number of the silyl group, and the carbon number is
usually in a range of 3 or more and 20 or less. The silicon number
is usually in a range of 1 or more and 6 or less.
[0050] --P(.dbd.O)R.sup.11R.sup.12 optionally has a substituent.
Examples of the substituent include an aryl group and a heteroaryl
group, and these substituents may be further substituted.
[0051] Any two adjacent substituents (e.g. R.sup.1 and R.sup.2 in
the general formula (1)) may be linked together to form a
conjugated or unconjugated fused ring. Particularly, formation of a
structure in which five fused rings are formed as a whole with
R.sup.1 and R.sup.2 forming a ring is preferable because charge
mobility is improved. As the structure in which five fused rings
are formed as a whole, benzo [a] naphthacene is especially
preferable. As constituent elements of the fused ring, an element
selected from nitrogen, oxygen, sulfur, phosphorus and silicon may
exist in addition to carbon. The fused ring may be further fused
with another ring.
[0052] R.sup.5 and R.sup.12 in the general formula (1) each
represent a group represented by the general formula (2) or
(3).
##STR00006##
In the general formula (2) or (3), R.sup.15 to R.sup.24 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl
group, a carbamoyl group, an amino group, a nitro group, a cyano
group, a silyl group and --P(.dbd.O)R.sup.13R.sup.14. R.sup.13 and
R.sup.14 each represent an aryl group or a heteroaryl group.
R.sup.16 to R.sup.19 and R.sup.21 to R.sup.24 may form a ring
between adjacent substituents. X represents an oxygen atom, a
sulfur atom or --NR.sup.25. R.sup.25 is hydrogen, an alkyl group, a
cycloalkyl group, a heterocyclic group, an aryl group or a
heteroaryl group.
[0053] It is preferable that as described above, two groups
represented by the general formula (2) or (3) exist at specific
bonding positions (5-position and 12-position) in a naphthacene
skeleton because both high charge mobility and high heat resistance
can be achieved, so that the photoelectric conversion efficiency
and durability of the photoelectric conversion element can be
improved.
[0054] A compound having a group represented by the general formula
(2) has high charge mobility because the compound has an aryl
group, so that charge transfer between molecules with .pi.
electrons is smoothed. Therefore, the compound considerably
contributes to an improvement in external quantum efficiency. It is
preferable that among groups represented by the general formula
(2), R.sup.15 is an alkyl group, an alkoxy group, an aryl group or
a heteroaryl group because the molecular interaction between
naphthacene skeletons is suppressed, so that high photoelectric
conversion efficiency can be achieved, and a stable thin film can
be formed. In particular, it is more preferable that R.sup.15 is an
alkyl group or alkoxy group with a carbon number of 1 to 20, or an
aryl group or heteroaryl group with a carbon number of 4 to 14
because acquirement of raw materials and the synthesis process
become easy, so that costs can be reduced. Further, it is
especially preferable that a naphthalene ring is formed as a whole
with R.sup.17 and R.sup.18 forming a ring because extremely
excellent charge mobility is achieved to contribute to an
improvement in external quantum efficiency.
[0055] A compound having a group represented by the general formula
(3) is preferable in that heat resistance is improved because the
compound has a bicyclic benzoheterocyclic ring, so that a high
glass transition temperature (Tg) can be secured. It is preferable
that among groups represented by the general formula (3),
R.sup.2.degree. is an alkyl group, an alkoxy group, an aryl group
or a heteroaryl group because the molecular interaction between
naphthacene skeletons is suppressed, so that high photoelectric
conversion efficiency can be achieved, and a stable thin film can
be formed. In particular, it is more preferable that
R.sup.2.degree. is an alkyl group or alkoxy group with a carbon
number of 1 to 20, or an aryl group or heteroaryl group with a
carbon number of 4 to 14 because acquirement of raw materials and
the synthesis process become easy, so that costs can be
reduced.
[0056] Examples of the alkyl group or alkoxy group with a carbon
number of 1 to 20 include a methyl group, an ethyl group, a
n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl
group, a tert-butyl group, a n-pentyl group, a cyclopentyl group, a
n-hexyl group, a cyclohexyl group, an adamantyl group, a methoxy
group, an ethoxy group, a n-propyloxy group, an isopropyloxy group,
a n-butoxy group, a sec-butoxy group, a tert-butoxy group, a
n-pentoxy group, a cyclopentoxy group, a n-hexyloxy group and a
cyclohexyloxy group. Among them, a methyl group, an ethyl group, a
n-propyl group, an isopropyl group, a n-butyl group, a tert-butyl
group and a methoxy group are preferable for securing both high
photoelectric conversion efficiency and thin film stability and
ease of acquirement of raw materials and the synthesis process.
[0057] Examples of the aryl group or heteroaryl group with a carbon
number of 4 to 14 include a phenyl group, a naphthyl group, a
phenanthryl group, an anthracenyl group, a fluorenyl group, a
furanyl group, a thiophenyl group, a pyrrolyl group, a benzofuranyl
group, a benzothiophenyl group, an indolyl group, a benzoxazolyl
group, a benzothiazolyl group, a benzimidazolyl group, a pyridyl
group, a quinolinyl group, a quinoxalinyl group, a carbazolyl group
and a venatololyl group. Among them, a phenyl group, a naphthyl
group, a phenanthryl group, a fluorenyl group, a benzofuranyl
group, a benzothiophenyl group, a pyridyl group, a quinolinyl group
and a quinoxalinyl group for securing both high photoelectric
conversion efficiency and thin film stability and ease of
acquirement of raw materials and the synthesis process.
[0058] The aryl group and heteroaryl group may further have a
substituent. As examples of the substituent here, alkyl groups such
as a methyl group, an ethyl group, a propyl group and a tert-butyl
group, alkoxy groups such as a methoxy group and an ethoxy group,
aryl ether groups such as a phenoxy group, aryl groups such as a
phenyl group, a naphthyl group and a biphenyl group, and heteroaryl
groups such as a pyridyl group, a quinolinyl group, a benzofuranyl
group and a benzothiophenyl group are preferable. Among them, a
methyl group, a tert-butyl group and a phenyl group are especially
preferable from the viewpoint of ease of acquirement of raw
materials and the synthesis process.
[0059] X in the general formula (3) is preferably an oxygen atom
because higher photoelectric conversion efficiency is obtained.
[0060] R.sup.1 to R.sup.4, R.sup.6 to R.sup.11, R.sup.16 to
R.sup.19 and R.sup.21 to R.sup.24 are each preferably hydrogen or
deuterium because vapor deposition becomes easier as the molecular
weight of the first compound decreases.
[0061] A known method can be used for synthesis of the first
compound represented by the general formula (1). Examples of the
method for introducing a group represented by the general formula
(2) or (3) into the naphthacene skeleton in the first compound
include, but are not limited to, a method using a coupling reaction
of a naphthoquinone derivative with an organic metal reagent, and a
method using a coupling reaction of a halogenated naphthacene
derivative with a boronic acid reagent under a palladium or nickel
catalyst.
[0062] Specific examples of the first compound represented by the
above general formula (1) may include the following compounds.
##STR00007## ##STR00008## ##STR00009## ##STR00010## ##STR00011##
##STR00012## ##STR00013## ##STR00014## ##STR00015## ##STR00016##
##STR00017## ##STR00018## ##STR00019## ##STR00020## ##STR00021##
##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026##
##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031##
##STR00032## ##STR00033## ##STR00034## ##STR00035## ##STR00036##
##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041##
##STR00042## ##STR00043## ##STR00044## ##STR00045##
##STR00046##
[0063] (Second Compound)
[0064] The second compound in which the maximum value of an
absorption coefficient at a wavelength of 400 to 700 nm is
5.times.10.sup.4 cm.sup.-1 or more in the present invention will be
described. When two or more maximum values of an absorption
coefficient exist at a wavelength of 400 to 700 nm, the maximum
value of an absorption coefficient, which is the largest of these
maximum values, is employed to make a judgement.
[0065] The first compound represented by the general formula (1)
has high charge mobility, and is therefore excellent in capability
of efficiently transporting generated charges to an electrode, but
on the other hand, the first compound has a small absorption
coefficient. Specifically, the absorption coefficient of the first
compound represented by the general formula (1), depending on a
type of substituent to be introduced into a naphthacene skeleton,
is 1.times.10.sup.4cm.sup.-1 to 5.times.10.sup.4 cm.sup.-1. This is
almost the same value as the absorption coefficient (about 10.sup.4
cm.sup.-1) of an inorganic thin film of silicon crystals etc.
Therefore, the first compound represented by the general formula
(1) cannot singly absorb incident light sufficiently, and thus most
of the light is transmitted, so that an optical loss occurs,
resulting in reduction of photoelectric conversion efficiency.
[0066] Meanwhile, as organic compounds to be used in the
photoelectric conversion layer, many compounds having a large
absorption coefficient of about 10.sup.5 to 10.sup.6 cm.sup.-1 are
known. For example, the compound A-1 shown below as an example has
an absorption coefficient of 1.16.times.10.sup.5 cm.sup.-1.
##STR00047##
[0067] Thus, high photoelectric conversion performance can be
achieved by employing a structure in which the organic layer
includes the first compound represented by the general formula (1),
and the second compound in which the maximum value of an absorption
coefficient at a wavelength of 400 to 700 nm is 5.times.10.sup.4
cm.sup.-1 or more. Namely, when the second compound having a large
absorption coefficient has a role of light absorption, and both the
first compound and the second compound have a role of charge
transfer, both light absorption property and charge mobility can be
secured, and therefore photoelectric conversion performance can be
exhibited.
[0068] Preferably, these compounds are contained particularly in
the photoelectric conversion layer in the organic layer. These
compounds are not necessarily contained only in the photoelectric
conversion layer. For example, the electron blocking layer and the
hole blocking layer may contain the first compound and the second
compound for improving the charge mobility of the layers or
increasing the number of carriers generated in the layers, or the
electron blocking layer and the hole blocking layer may contain the
second compound for improving the light absorption property of the
whole photoelectric conversion element.
[0069] The absorption coefficient of the second compound is
preferably as large as possible. For obtaining efficiency for light
utilization, which is higher than that of an inorganic
photoelectric conversion element, by making use of high light
absorption property that is specific to an organic photoelectric
conversion element, the absorption coefficient is preferably
5.times.10.sup.4 cm.sup.-1 or more, more preferably
8.times.10.sup.4 cm.sup.-1 or more, still more preferably
1.times.10.sup.5 cm.sup.-1 or more.
[0070] As a material having an absorption coefficient as described
above, a pigment-based material is suitable because of good light
absorption property. Specific examples thereof include derivatives
of merocyanine, coumarin, nile red, rhodamine, oxazine, acridine,
squarylium, diketo-pyrrolo-pyrrole, pyrromethene, pyrene, perylene,
thiophene, phthalocyanine and so on. Further, when the
photoelectric conversion element of the present invention is used
as an image sensor, a material having a single absorption peak at a
wavelength of 400 to 700 nm is suitably used. Specific examples of
the material having an absorption as described above and having a
large absorption coefficient of 1.times.10.sup.5 cm.sup.-1 or more
include thiophene derivatives, pyrene derivatives and perylene
derivatives.
[0071] The thiophene derivative is preferably a compound
represented by the general formula (4).
##STR00048##
[0072] In the general formula (4), R.sup.25 to R.sup.28 may be the
same or different, and each represent a group selected from the
group consisting of hydrogen, an alkyl group, a cycloalkyl group, a
heterocyclic group, an alkenyl group, a cycloalkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, an aryl ether
group, an aryl thioether group, an aryl group, a heteroaryl group,
a halogen, an amino group, a silyl group, --P(.dbd.O)
R.sup.29R.sup.30, and a group represented by the following general
formula (5). R.sup.29 and R.sup.30 each represent an aryl group or
a heteroaryl group. m represents an integer of 1 to 6. At least one
of R.sup.25 to R.sup.28 represents a group represented by the
following general formula (5).
[Chemical Formula 20]
-L CN).sub.n (5)
[0073] In the general formula (5), n represents 1 or 2. L
represents an alkenediyl group, an arylenediyl group or a
heteroarylenediyl group when n represents 1. L represents an
aklenetriyl group, an arylenetriyl group or a heteroarylenetriyl
group when n represents 2.
[0074] The compound represented by the general formula (4) is a
compound having a high light absorption coefficient, a single peak
absorption, and good color selectivity. When m is an integer of 1
to 6, the compound has an absorption region in a wavelength range
of 400 to 700 nm. For example, when a photoelectric conversion
element having an absorption in a green region is produced, m is
preferably 2 to 4, especially preferably 3. By appropriately
selecting the types of substituents of R.sup.25 to R.sup.28, the
absorption wavelength can be more reliably controlled. When the
first compound is used as a p-type semiconductor material, the
second compound being a compound represented by the general formula
(4) serves as a n-type semiconductor material having good
electron-transporting property when at least one of R.sup.25 to
R.sup.28 is a group represented by the general formula (5).
[0075] The pyrene derivative is preferably a compound represented
by the general formula (6).
##STR00049##
[0076] R.sup.31 to R.sup.34 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, an amino
group, a silyl group, --P(.dbd.O)R.sup.35R.sup.36, and a group
represented by the following general formula (5). R.sup.35 and
R.sup.36 each represent an aryl group or a heteroaryl group. At
least one of R.sup.31 to R.sup.34 represents a group represented by
the following general formula (5).
[Chemical Formula 22]
-L CN).sub.n (5)
[0077] In the general formula (5), n represents 1 or 2. L
represents an alkenediyl group, an arylenediyl group or a
heteroarylenediyl group when n represents 1. L represents an
aklenetriyl group, an arylenetriyl group or a heteroarylenetriyl
group when n represents 2.
[0078] The compound represented by the general formula (6) is a
compound having a single peak absorption, and good color
selectivity. By appropriately selecting the types of substituents
of R.sup.31 to R.sup.34, the absorption wavelength can be more
reliably controlled. Particularly, it is preferable that at least
one of R.sup.31 to R.sup.34 is a group represented by the general
formula (5) because the compound has an absorption region in a
wavelength range of 400 to 700 nm, and serves as a n-type
semiconductor material having good electron-transporting
property.
[0079] The perylene derivative is preferably a compound represented
by the general formula (7).
##STR00050##
[0080] R.sup.37 and R.sup.38 may be the same or different, and each
represent a group selected from the group consisting of hydrogen,
an alkyl group, a cycloalkyl group, a heterocyclic group, an
alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, an aryl ether group, an aryl thioether
group, an aryl group, a heteroaryl group, a halogen, an amino
group, a cyano group, a silyl group and
--P(.dbd.O)R.sup.39R.sup.40. R.sup.39 and R.sup.40 each represent
an aryl group or a heteroaryl group.
[0081] The compound represented by the general formula (7) is a
compound having a high light absorption coefficient and good color
selectivity. By appropriately setting the types of substituents of
R.sup.37 and R.sup.38, the absorption wavelength can be controlled.
The compound represented by the general formula (7) is preferably
used as a n-type semiconductor because it has good
electron-transporting property.
[0082] The absorption coefficient herein means a ratio of light
absorbed per unit length when the light passes through a thin film.
The absorption coefficient is a value calculated by substituting
relevant values in the formula of (absorbency)/(thickness).
Specifically, an organic compound is deposited with a thickness of
50 nm at a deposition rate of 1 .ANG./second on a 0.7 mm-thick
transparent quartz glass using a vacuum vapor deposition method, an
absorbency in a visible region of 400 nm to 700 nm is measured by
an ultraviolet/visible spectrophotometer, and the maximum value of
the absorbency is then divided by the thickness (unit: cm) of an
organic compound to calculate an absorption coefficient.
[0083] The first compound represented by the general formula (1)
can be used either as a p-type semiconductor material or as a
n-type semiconductor material according to relative magnitudes of
an ionization potential and electron affinity with respect to the
second compound, but the first compound represented by the general
formula (1) is preferably used as a p-type semiconductor material.
The first compound represented by the general formula (1) is
preferably used as a p-type semiconductor material particularly
because the compound contains a group represented by the general
formula (2) or (3), and is therefore excellent in hole transport
property. The second compound is preferably a n-type semiconductor
material.
[0084] The p-type semiconductor material as used herein represents
a hole-transporting semiconductor material which has
electron-donating property, and easily releases electrons (i.e. the
p-type semiconductor material has a small ionization potential).
The n-type semiconductor material represents an
electron-transporting semiconductor material which has
electron-accepting property, and easily accepts electrons (i.e. the
n-type semiconductor material has high electron affinity). When the
photoelectric conversion layer is composed of a p-type
semiconductor material and a n-type semiconductor material, charges
can be efficiently separated into holes and electrons before
excitons produced by incident light in the photoelectric conversion
layer returns to a ground state. Holes and electrons thus separated
flow to the cathode and the anode through the p-type semiconductor
material and the n-type semiconductor material, respectively, so
that high photoelectric conversion efficiency can be achieved.
[0085] Electrodes and organic layers that form the photoelectric
conversion element will now be described.
[0086] (Cathode and Anode)
[0087] In the photoelectric conversion element of the present
invention, the cathode and the anode have a role of ensuring that
electrons and holes produced in the photoelectric conversion
element can flow to sufficiently feed a current. Preferably, at
least one of the cathode and the anode is transparent or
semitransparent for allowing light to be incident. Usually, a
transparent electrode is used as the cathode to be formed on the
substrate.
[0088] The cathode may be transparent for making it possible to
extract holes from the photoelectric conversion layer and allowing
light to be incident. When the cathode is a transparent electrode,
the material of the cathode is preferably a conductive metal oxide
such as tin oxide, indium oxide or indium tin oxide (ITO); a metal
such as gold, silver or chromium; an inorganic conductive substance
such as copper iodide or copper sulfide; a conductive polymer such
as polythiophene, polypyrrole or polyaniline; or the like. When the
cathode is used as a transparent electrode, it is especially
preferable to use ITO glass with ITO on a grass substrate surface,
or NESA glass with silver oxide on a glass substrate surface.
[0089] The transparent electrode may have resistance that allows a
current produced in the photoelectric conversion element to
sufficiently flow, and low resistance is preferable from the
viewpoint of photoelectric conversion efficiency of the
photoelectric conversion element. For example, an ITO substrate
having a resistance of 300 WE or less serves as an element
electrode, and therefore it is especially preferable to use a
low-resistance product. The thickness of ITO or silver oxide can be
appropriately selected according to the resistance value, and is
commonly in a range of 50 to 300 nm. Soda-lime glass, alkali-free
glass or the like is used for the glass substrate of ITO glass or
NESA glass. The thickness of the glass substrate may have a
thickness sufficient to maintain mechanical strength, and therefore
a thickness of 0.5 mm or more is sufficient. The lesser ions eluted
from the glass substrate, the better, so that the material of the
glass substrate is preferably alkali-free glass, and soda-lime
glass subjected to SiO.sub.2 barrier coating can also be used. If
the cathode stably functions, there is no need that the substrate
be made of glass and, for example, a cathode may be formed on a
plastic substrate. Examples of the method for formation of an ITO
film include, but are not limited to, an electron beam method, a
sputtering method, a chemical reaction method, and the like.
[0090] Preferably, the anode is made of a substance capable of
efficiently extracting electrons from the photoelectric conversion
layer, and examples thereof include platinum, gold, silver, copper,
iron, tin, zinc, aluminum, indium, chromium, lithium, sodium,
potassium, calcium, magnesium, cesium, and strontium. To improve
element characteristics by enhancing electron extraction
efficiency, lithium, sodium, potassium, calcium, magnesium, and
cesium, or alloys containing these low work-function metals are
effective. However, these low work-function metals are often
unstable in the air in general, and it is possible to exemplify, as
a preferable example, a method in which an electrode having high
stability is used after doping the hole blocking layer with a trace
amount of lithium, magnesium, or cesium (1 nm or less displayed by
a film thickness meter of vacuum vapor deposition). It is also
possible to use an inorganic salt such as lithium fluoride. To
protect the electrode, it is preferred to laminate metals such as
platinum, gold, silver, copper, iron, tin, aluminum, and indium, or
alloys using these metals; inorganic substances such as silica,
titania, and silicon nitride; polyvinyl alcohol, vinyl chloride,
hydrocarbon-based polymers, and the like. The method for production
of these electrodes is preferably a method capable of securing
conduction, such as resistance heating, electron beam, sputtering,
ion plating or coating.
[0091] When the photoelectric conversion element of the present
invention is used as an image sensor, application of an electric
field between the anode and the cathode from the outside produces
an effect of improving photoelectric conversion efficiency because
electrons and holes generated in the photoelectric conversion layer
are easily guided to the anode side and the cathode side,
respectively. Here, the applied voltage is preferably 10.sup.5 V/m
or more and 10.sup.9 V/m or less. When the applied voltage is
10.sup.5 V/m or more, generated charges are easily transported
efficiently, and therefore photoelectric conversion efficiency is
hardly reduced. When the applied voltage is 10.sup.9 V/m or less, a
dark current is reduced, so that the S/N ratio is improved, and the
probability of occurrence of current leakage decreases. Even when
an electric field is not applied between the anode and the cathode,
charges are caused to flow to the photoelectric conversion element
by an internal electric field at the time of connecting the anode
and the cathode to make a closed circuit, and therefore it is also
possible to use the photoelectric conversion element as a
photovoltatic element.
[0092] (Photoelectric Conversion Layer)
[0093] The photoelectric conversion layer is a layer that causes
photoelectric conversion in which incident light is absorbed to
generate charges. The photoelectric conversion layer may be
composed of one photoelectric conversion material, and is
preferably composed of a p-type semiconductor material and a n-type
semiconductor material. Here, the photoelectric conversion layer
may include one or more p-type semiconductor material(s) and one or
more n-type semiconductor material(s). In the photoelectric
conversion layer, the photoelectric conversion material absorbs
light to form excitons, and electrons and holes are then separated
by the n-type semiconductor material and the p-type semiconductor
material, respectively. Electrons and holes thus separated are
caused to flow to both the electrodes through a conduction level
and a valence level, so that electric energy is produced.
[0094] As a structure of the photoelectric conversion layer, a bulk
heterojunction with the first compound and second compound mixed in
the same layer by a method such as co-deposition is preferable. The
bulk heterojunction is a structure in which two or more compounds
are randomly mixed in one layer, and the compounds are joined
together at a nano-level. Accordingly, charges generated in one of
the materials can be efficiently separated into holes and
electrons. For exhibiting high light-absorbing property, the
absorption coefficient of the mixed film of the first compound and
the second compound is preferably 5.times.10.sup.4 cm.sup.-1 or
more, more preferably 8.times.10.sup.4 cm.sup.-1 or more, still
more preferably 1.times.10.sup.5 cm.sup.-1 or more.
[0095] Since the absorption coefficient of the whole thin film and
the carrier-transporting property presented by the second compound
are reduced as the mixing ratio of the first compound is increased,
and the carrier property presented by the first compound is reduced
as the mixing ratio of the second compound is increased, the mixing
ratio of the first compound represented by the general formula (1)
and the second compound (first compound:second compound) is
preferably in a range of 75%:25% to 25%:75% in terms of a molar
ratio. When the second compound having a large absorption
coefficient is contained in a larger amount, the absorption
coefficient of the whole thin film is improved, leading to
improvement of photoelectric conversion efficiency, and therefore
the mixing ratio of the first compound and the second compound
(first compound:second compound) is more preferably in a range of
50%:50% to 25%:75%.
[0096] The first compound and the second compound are each required
to have a function of efficiently transporting generated charges
for obtaining high photoelectric conversion efficiency. The charge
mobility of each of the first compound and the second compound is
preferably 1.times.10.sup.-9 cm.sup.2/Vs or more, more preferably
1.times.10.sup.-8 cm.sup.2/Vs or more, still more preferably
1.times.10.sup.-7 cm.sup.2/Vs or more.
[0097] The charge mobility herein is mobility measured by a space
charge limited current method (SCLC method) (see, for example, Adv.
Funct. Mater, Vol.16 (2006), page 701 as a reference).
[0098] When the thickness of the organic layer is excessively
small, the probability of occurrence of current leakage becomes
higher, and the number of carriers generated decreases under the
influence of thinning of the photoelectric conversion layer, so
that photoelectric conversion efficiency is reduced. When the
thickness of the organic layer is excessively large, carriers
generated in the photoelectric conversion layer hardly arrive at
the electrode, so that photoelectric conversion efficiency is
reduced, and a higher electric field is required, leading to an
increase in power consumption. Therefore, the thickness of the
organic layer is preferably 20 nm or more and 200 nm or less.
[0099] For the photoelectric conversion material that forms the
photoelectric conversion layer, a material previously known as a
photoelectric conversion material may be used in combination in
addition to the first compound and the second compound. When the
first compound and the second compound are used in an organic layer
other than the photoelectric conversion layer, materials previously
known as photoelectric conversion materials can be used alone or in
combination thereof.
[0100] The absorption wavelength of the photoelectric conversion
layer is determined by the light absorption wavelength region of
the photoelectric conversion material, so that it is preferable to
use a material having light absorption characteristics
corresponding to the color intended for use. For example, in the
green photoelectric conversion element, the photoelectric
conversion layer is composed of a material which absorbs light at a
wavelength of 490 nm to 570 nm. When the photoelectric conversion
layer is composed of two or more materials, and contain a p-type
semiconductor material and a n-type semiconductor material, holes
and electrons can be efficiently separated because among carriers
generated in the photoelectric conversion layer, holes are apt to
flow through the p-type semiconductor material, and electrons are
apt to flow through the n-type semiconductor material. Therefore,
for obtaining high photoelectric conversion efficiency, the
photoelectric conversion layer is composed of a material including
a p-type semiconductor material and a n-type semiconductor material
which have mutually different energy levels, and the photoelectric
conversion layer is composed of a material having high charge
mobility so that holes and electrons generated in the photoelectric
conversion layer can transfer to the electrode side.
[0101] The p-type semiconductor material may be any organic
compound as long as it is a hole-transporting compound which has
comparatively small ionization potential and has electron-donating
property. Examples of the p-type organic semiconductor material
include compounds including fused polycyclic aromatic derivatives
such as naphthalene, anthracene, phenanthrene, pyrene, chrysene,
naphthacene, triphenylene, perylene, fluoranthene, fluorene,
indene, and derivatives thereof; cyclopentadiene derivatives, furan
derivatives, thiophene derivatives, pyrrole derivatives, benzofuran
derivatives, benzothiophene derivatives, indole derivatives,
pyrazoline derivatives, dibenzofuran derivatives, dibenzothiophene
derivatives, carbazole derivatives, indolocarbazole derivatives;
aromatic amine derivatives such as [0102]
N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine;
styrylamine derivatives, benzidine derivatives, porphyrin
derivatives, phthalocyanine derivatives and quinacridone
derivatives.
[0103] Examples of the polymer-based material include, but are not
particularly limited to, polyphenylenevinylene derivatives,
polyparaphenylene derivatives, polyfluorene derivatives,
polyvinylcarbazole derivatives, and polythiophene derivatives.
[0104] The n-type semiconductor material may be any material as
long as it is an electron-transporting compound having high
electron affinity. Examples of the n-type semiconductor material
include fused polycyclic aromatic derivatives such as naphthalene,
anthracene and naphthacene; styryl-based aromatic ring derivatives
typified by [0105] 4,4'-bis(diphenylethenyl)biphenyl,
tetraphenylbutadiene derivatives, coumarin derivatives, oxadiazole
derivatives, pyrrolopyridine derivatives, perinone derivatives,
pyrrolopyrrole derivatives, thiadiazolopyridine derivatives,
aromatic acetylene derivatives, aldazine derivatives, pyrromethene
derivatives, diketopyrrolo[3,4-c]pyrrole derivatives; azole
derivatives such as imidazole, thiazole, thiadiazole, oxazole,
oxadiazole, and triazole, and metal complexes thereof; quinone
derivatives such as anthraquinone and diphenoquinone; phosphorus
oxide derivatives, and quinolinol complexes such as [0106]
tris(8-quinolinolate)aluminum(III); and various metal complexes
such as benzoquinolinol complex, hydroxyazole complex, azomethine
complex, tropolone-metal complex, and flavonol-metal complex.
[0107] Further, examples of the n-type semiconductor material
include organic compounds having a nitro group, a cyano group,
halogen, or a trifluoromethyl group in the molecule; acid
anhydride-based compounds such as quinone-based compound, maleic
anhydride, and phthalic anhydride; and fullerene and fullerene
derivatives, such as C60 and PCBM.
[0108] Further, examples of the n-type semiconductor material
include compounds having a heteroaryl ring structure which is
composed of elements selected from hydrogen, nitrogen, oxygen,
silicon and phosphorus, and contains electron-accepting nitrogen.
The electron-accepting nitrogen as used herein represents a
nitrogen atom which forms a multiple bond with an adjacent atom.
Since a nitrogen atom has high electronegativity, the multiple bond
has electron-accepting property. Therefore, an aromatic
heterocyclic ring containing electron-accepting nitrogen has high
electron affinity, and is thus preferable as a n-type semiconductor
material.
[0109] Examples of the heteroaryl ring containing
electron-accepting nitrogen include pyridine rings, pyrazine rings,
pyrimidine rings, quinoline rings, quinoxaline rings, naphthyridine
rings, pyrimidopyrimidine rings, benzoquinoline rings,
phenanthroline rings, imidazole rings, oxazole rings, oxadiazole
rings, triazole rings, thiadiazole rings, benzoxazole rings,
benzothiazole rings, benzimidazole rings and phenanthroimidazole
rings.
[0110] Examples of the preferred compound having such a heteroaryl
ring structure include benzimidazole derivatives, benzoxazole
derivatives, benzthiazole derivatives, oxadiazole derivatives,
thiadiazole derivatives, triazole derivatives, pyrazine
derivatives, phenanthroline derivatives, quinoxaline derivatives,
quinoline derivatives, benzoquinoline derivatives, oligopyridine
derivatives such as bipyridine and terpyridine, quinoxaline
derivatives and naphthyridine derivatives. Among them, imidazole
derivatives such as tris(N-phenylbenzimidazole-2-yl)benzene,
oxadiazole derivatives such as [0111]
1,3-bis[(4-tert-butylphenyl)1,3,4-oxadiazolyl]phenylene, triazole
derivatives such as [0112] N-naphthyl-2,5-diphenyl-1,3,4-triazole,
phenanthroline derivatives such as bathocuproin and [0113]
1,3-bis(1,10-phenanthroline-9-yl)benzene, benzoquinoline
derivatives such as [0114]
2,2'-bis(benzo[h]quinoline-2-yl)-9,9'-spirobifluorene, bipyridine
derivatives such as [0115]
2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole,
terpyridine derivatives such as [0116]
1,3-bis(4'-(2,2':6'2''-terpyridinyl))benzene, naphthyridine
derivatives such as [0117]
bis(1-naphthyl)-4-(1,8-naphthyridine-2-yl)phenylphosphine oxide,
and the like are preferably used from the viewpoint of an
electron-transporting ability.
[0118] Preferred n-type semiconductor materials that can be used
include, but are not limited to, a group of the above-mentioned
materials.
[0119] (Charge Blocking Layer)
[0120] The charge blocking layer is a layer for taking out
electrons and holes photoelectrically converted by the
photoelectric conversion layer in an efficient and stable manner,
and examples thereof include an electron blocking layer for
blocking electrons and a hole blocking layer for blocking holes.
These layers may be composed of an inorganic substance or an
organic compound. These layers may also be composed of a mixed
layer of an inorganic substance and an organic compound.
[0121] The hole blocking layer is a layer for blocking
recombination of holes produced in the photoelectric conversion
layer with electrons as a result of flow of holes to the anode
side. According to types of the material composing each layer,
recombination of holes with electrons is suppressed by inserting
this layer, leading to an improvement in photoelectric conversion
efficiency. Thus, the hole blocking material preferably has an HOMO
level which is energetically lower than that of the photoelectric
conversion material. A compound capable of efficiently blocking
transfer of holes from the photoelectric conversion layer is
preferable, and specific examples thereof include quinolinol
derivative metal complexes typified by 8-hydroxyquinoline aluminum;
tropolone-metal complexes, flavonol-metal complexes, perylene
derivatives, perinone derivatives, naphthalene derivatives,
coumarin derivatives, oxadiazole derivatives, aldazine derivatives,
bisstyryl derivatives, and pyrazine derivatives; oligopyridine
derivatives such as bipyridine and terpyridine; phenanthroline
derivatives, quinoline derivatives and aromatic phosphorus oxide
compounds. These hole blocking materials may be used alone, or
different hole blocking materials may be used in a state of being
laminated or mixed.
[0122] The electron blocking layer is a layer for blocking
recombination of electrons produced in the photoelectric conversion
layer with holes as a result of flow of holes to the cathode side.
According to types of the material composing each layer,
recombination of holes with electrons is suppressed by inserting
this layer, leading to an improvement in photoelectric conversion
efficiency. Thus, the electron blocking material preferably has an
LUMO level which is energetically higher than that of the
photoelectric conversion material. A compound capable of
efficiently blocking transfer of electrons from the photoelectric
conversion layer is preferable, and specific examples thereof
include triphenylamines such as [0123]
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4-diphenyl-1,1'-diamine
and [0124]
N,N'-bis(1-naphthyl)-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine;
bis(N-allylcarbazole) or bis(N-alkylcarbazole), [0125] pyrazoline
derivatives, stilbene-based compounds, distyryl derivatives,
hydrazone-based compounds; and heterocyclic compounds typified by
oxadiazole derivatives, phthalocyanine derivatives, and porphyrin
derivatives. Examples of the polymer-based material include
polycarbonate and styrene derivatives containing the monomer in the
side chain, polyvinylcarbazole and polysilane. It is desirable to
use a compound which forms a thin film required for production of
the photoelectric conversion element and can extract holes from the
photoelectric conversion layer, and also can transport holes. These
electron blocking materials may be used alone, or different
electron blocking materials may be used in a state of being
laminated or mixed.
[0126] The above hole blocking layers and electron blocking layers
can be used alone, or two or more of the materials can be used in a
state of being laminated or mixed. It is also possible to use the
hole blocking layer and the electron blocking layer in a state of
being dispersed in solvent-soluble resins such as polyvinyl
chloride, polycarbonate, polystyrene, poly(N-vinylcarbazole),
polymethyl methacrylate, polybutyl methacrylate, polyester,
polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin,
ketone resin, phenoxy resin, polysulfone, polyamide, ethyl
cellulose, vinyl acetate, ABS resin, and polyurethane resin; and
curable resins such as phenol resin, xylene resin, petroleum resin,
urea resin, melamine resin, unsaturated polyester resin, alkyd
resin, epoxy resin, and silicone resin; as a polymer binder.
[0127] Examples of the method for formation of an organic layer
include, but are not limited to, a resistance heating vapor
deposition method, an electron beam vapor deposition method, a
sputtering method, a molecular lamination method, a coating method,
and the like, and usually, the method is preferably a resistance
heating vapor deposition method or an electron beam vapor
deposition method in view of characteristics.
[0128] <Image Sensor>
[0129] The photoelectric conversion element of the present
invention can be suitably used in an image sensor. The image sensor
is a semiconductor element for converting an optical image into
electrical signal. In general, the image sensor is composed of the
above-mentioned photoelectric conversion element for converting
light into electric energy, and a circuit for reading out electric
energy in the form of electrical signal. According to applications
of the image sensor, a plurality of photoelectric conversion
elements can be aligned on one-dimensional straight line or
two-dimensional plane. A monocolor image sensor may be composed of
one photoelectric conversion element, but a color image sensor is
composed of two or more photoelectric conversion elements. For
example, the color image sensor is composed of a photoelectric
conversion element for detecting red light, a photoelectric
conversion element for detecting green light, and a photoelectric
conversion element for detecting blue light. Photoelectric
conversion elements of different colors have a laminated structure.
Namely, the photoelectric conversion elements may be laminated on
one pixel, or arranged side by side to form a matrix structure.
[0130] In the case of a structure in which a photoelectric
conversion element is laminated on one pixel, as shown in FIG. 5,
the structure may be a three-layer structure in which a
photoelectric conversion element for detecting green light 32, a
photoelectric conversion element for detecting blue light 33, and a
photoelectric conversion element for detecting red light 31 are
sequentially laminated. Alternatively, as shown in FIG. 6, the
structure may be a two-layer structure in which a photoelectric
conversion element for detecting green light 32 is disposed on the
whole surface of an upper layer, and a photoelectric conversion
element for detecting red light 31 and a photoelectric conversion
element for detecting blue light 33 are formed in the form of a
matrix structure. These structures are those in which the
photoelectric conversion element 32 for detecting green light is
disposed on a layer which is the nearest to incident light 34. The
order of lamination of each color is not limited thereto, and may
be different from that in FIG. 5. For ensuring that a photoelectric
conversion element as an outer most layer serves as a color filter
which absorbs light of specific color, and transmits
long-wavelength light and short-wavelength light other than the
light of specific color, a structure in which a green photoelectric
conversion element is disposed as the outermost layer is
preferable. When the blue photoelectric conversion element has
excellent color selectivity, it is possible to use a structure in
which the blue photoelectric conversion element is disposed as an
uppermost layer from a viewpoint of ease of detecting a short
wavelength.
[0131] In the case of a matrix structure, the array of
photoelectric conversion elements can be selected from arrays such
as Bayer array, honeycomb array, striped array, and delta array. An
organic photoelectric conversion material is used in a
photoelectric conversion element for detecting green light, and it
is possible to appropriately use inorganic photoelectric conversion
materials and organic photoelectric conversion materials, which
have hitherto been used, in combination as for the photoelectric
conversion element for detecting red light and the photoelectric
conversion element for detecting blue light.
[0132] <Solar Cell>
[0133] The photoelectric conversion element of the present
invention can be used in a solar cell. The solar cell is an energy
conversion element which absorbs energy of sunlight and converts
the energy of sunlight directly into electricity. The solar cell
has a principle in common with an image sensor in that light is
absorbed to generate electric energy, but the solar cell is
different from the image sensor in that in the image sensor,
charges generated in a photoelectric conversion layer are easily
extracted by usually applying an electric field from the outside,
whereas in the solar cell, a photoelectric conversion element
itself generates photovoltatic power, so that charges generated in
a photoelectric conversion layer are extracted to the outside.
[0134] The photoelectric conversion element of the present
invention is suitable for conversion of light mainly in a visible
region into electric energy because the photoelectric conversion
element contains a compound that absorbs light having a wavelength
of 400 to 700 nm. For improving the conversion efficiency of the
solar cell, it is preferable to absorb light in a wavelength region
that is as wide as possible. Therefore, a compound having
light-absorbing property in the whole wavelength region of 400 to
700 nm is preferably used particularly as the second compound
having a high light absorption coefficient. When the light
absorption wavelength region is narrow in the photoelectric
conversion element of the present invention, photoelectric
conversion elements with mutually different light absorption
wavelength regions (e.g. photoelectric conversion elements that
absorb light of red, green and blue, respectively) may be laminated
in a vertical form to produce a solar cell having a tandem
structure.
[0135] <Single Color Detection Sensor>
[0136] The photoelectric conversion element of the present
invention can be used in a single color detection sensor. The
photoelectric conversion element can be suitably used in a single
color detection sensor particularly when the photoelectric
conversion element has color selectivity/color discriminability and
a high light absorption coefficient. The single color detection
sensor can be applied to remote controllers for televisions and
electric appliances, light receiving elements for compact
displayers, illuminance sensors, fluorescent probe sensors, CCDs,
photoresistors and so on, but the application of the single color
detection sensor is not limited thereto.
[0137] <Flexible Sensor>
[0138] The photoelectric conversion element of the present
invention can be used in a flexible sensor. A photoelectric
conversion element using an organic compound is lighter and more
flexible than an existing photoelectric conversion element using an
inorganic semiconductor. By making use of this feature, the
photoelectric conversion element can be mounted on a curved-surface
structure, or mounted for imaging a surface of a living body. Since
the photoelectric conversion element can be produced in a printing
process, a sensor with a large area can be produced.
EXAMPLES
[0139] The present invention will be described below by way of
Examples, but the present invention is not limited to these
Examples. The number of each compound in the following Examples
indicates the number of each of the foregoing compounds. Evaluation
methods with respect to structural analysis are shown below.
[0140] Using superconductive FTNMR EX-270 (manufactured by JEOL,
Ltd.), .sup.1H-NMR was measured by a deuterated chloroform
solution.
[0141] Using a U-3200 type spectrophotometer (manufactured by
Hitachi, Ltd.), an absorption spectrum was measured after vapor
deposition of a sample in a film thickness of 50 nm on a quartz
substrate. An absorption coefficient was calculated by Lambert-Beer
Law.
[0142] The spectral sensitivity characteristics (external quantum
efficiency and maximum sensitivity wavelength) of a photoelectric
conversion element were measured using a spectral sensitivity
measurement system Model SM-250 (manufactured by Bunkoukeiki Co.,
Ltd.).
Synthesis Example 1
[0143] Method for Synthesis of Compound [10]
[0144] A mixed solution of phenylacetylene (10.0 g) and dehydrated
tetrahydrofuran (200 ml) was stirred at 0.degree. C. under a
nitrogen gas flow. To this mixed solution was added dropwise
n-butyllithium (1.6 M hexane solution (62 ml)), and the mixture was
then stirred at 0.degree. C. for 2 hours. Thereafter, a mixed
solution of phenylacetaldehyde (6.0 g) and dehydrated
tetrahydrofuran (20 ml) was added dropwise, and the mixture was
then returned to room temperature, and stirred for 4 hours. To the
reaction solution was added pure water (100 ml), and the mixture
was then extracted with ethyl acetate. The thus obtained solution
was dried over magnesium sulfate and, after filtration, the solvent
was distilled off. The thus obtained liquid was purified by silica
gel column chromatography, and evaporated to obtain a yellow liquid
(9.0 g).
[0145] Next, a mixed solution of the yellow liquid (9. 0 g), sodium
bicarbonate (6.8 g), iodine (30.8 g) and acetonitrile (400 ml) was
stirred at room temperature for 4 hours under a nitrogen flow. To
the reaction solution was added a saturated sodium thiosulfate
aqueous solution (100 ml), and the mixture was stirred for 1 hour,
and then extracted with ethyl acetate. The thus obtained solution
was dried over magnesium sulfate and, after filtration, the solvent
was distilled off. The thus obtained liquid was purified by silica
gel column chromatography, and evaporated to obtain a yellow liquid
(9.3 g)
[0146] Next, a mixed solution of the yellow liquid (9.3 g) and
dehydrated tetrahydrofuran (56 ml) was stirred at -78.degree. C.
under a nitrogen flow. To this mixed solution was added dropwise
n-butyllithium (1.6 M hexane solution (19 ml)), and the mixture was
then stirred at -78.degree. C. for 2 hours. To the reaction
solution was added 5,12-naphthacenequinone (2.9 g) for 30 minutes,
and the mixture was then stirred at room temperature for 4 hours.
To the reaction solution was added pure water (100 ml), and the
mixture was evaporated to remove a half of the tetrahydrofuran, and
then extracted with dichloromethane. The thus obtained solution was
dried over magnesium sulfate and, after filtration, the solvent was
distilled off. The thus obtained solid was dissolved in a small
amount of dichloromethane, and then precipitated by adding
methanol, and the mixture was filtered.
[0147] The thus obtained solid was vacuum-dried to obtain a yellow
powder (2.8 g).
[0148] Next, a mixed solution of the yellow powder (2.8 g) and
dehydrated tetrahydrofuran (43 ml) was stirred at 40.degree. C.
under a nitrogen flow. To this mixed solution were added dropwise
concentrated hydrochloric acid (22.4 ml) and tin chloride (II)
dihydrate (9.6 g), and the mixture was then stirred for 4 hours.
The reaction solution was returned to room temperature, methanol
(100 ml) was then added, and the mixture was stirred for 30
minutes, and then filtered. The thus obtained solid was washed with
pure water and methanol, and then filtered. The thus obtained solid
was purified by silica gel column chromatography, and evaporated to
obtain an orange powder (550 mg).
[0149] The results of .sup.1H-NMR analysis of the thus-obtained
powder are as follows, and show that the thus obtained orange
powder is a compound [10].
[0150] .sup.1H-NMR (CDCl.sub.3 (d=ppm)): 6.70-7.74 (m, 26H),
8.04-9.09 (t, 4H), 8.19 (s, 2H).
[0151] Light absorption characteristics of the compound [10] are as
follows. [0152] Maximum absorption wavelength: 504 nm (thin film:
50 nm) [0153] Full width at half maximum at maximum absorption
wavelength: 23 nm [0154] Absorption coefficient at maximum
absorption wavelength: 4.72.times.10.sup.4 cm.sup.-1
Synthesis Example 2
[0155] Method for Synthesis of Compound [43]
[0156] A mixed solution of 2-bromoacetophenone (35.0 g), phenol
(18.2 g), potassium carbonate (26.7 g) and acetone (700 ml) was
refluxed for 5 hours under a nitrogen flow. The reaction solution
was returned to room temperature, evaporated to remove the solvent,
and then extracted with toluene. The thus obtained solution was
dried over magnesium sulfate, and then evaporated to remove the
solvent. The thus obtained solid was recrystallized with methanol
to obtain a white powder (23.0 g).
[0157] Next, a mixed solution of the white powder (23.0 g),
methanesulfonic acid (52.0 g) and toluene (430 ml) was stirred at
80.degree. C. for 6 hours under a nitrogen flow. The reaction
solution was returned to room temperature, pure water (400 ml) was
added, and the mixture was stirred for 30 minutes, and then
extracted with toluene. The thus obtained solution was dried over
magnesium sulfate, and then evaporated to remove the solvent. The
thus obtained solution was purified by silica gel column
chromatography, and evaporated to obtain a colorless liquid (19.0
g).
[0158] Next, a mixed solution of the colorless liquid (19.0 g) and
dehydrated tetrahydrofuran (200 ml) was stirred at 0.degree. C.
under a nitrogen flow. To this mixed solution was added dropwise
n-butyllithium (1.6 M hexane solution (61 ml)), and the mixture was
then stirred at 0.degree. C. for 3 hours. To the reaction solution
was added 5,12-naphthacenequinone (10.1 g) for 30 minutes, and the
mixture was then stirred at 0.degree. C. for 1 hour. The reaction
solution was returned to room temperature, and further stirred for
1 hour, pure water (200 ml) and toluene (200 ml) were then added,
and the mixture was stirred for 30 minutes. The organic layer was
separated, and then dried over magnesium sulfate, and evaporated to
remove the solvent. The thus obtained solid was recrystallized with
toluene to obtain a white powder (21.4 g).
[0159] Next, a mixed solution of the white powder (21.4 g), sodium
hypophosphite monohydrate (34.9 g), potassium iodide (36.2 g) and
acetic acid (330 ml) was refluxed for 2 hours under a nitrogen
flow. To the reaction solution was added pure water (350 ml), and
the mixture was stirred for 30 minutes, and then filtered. To the
thus obtained solid was added cyclopentyl methyl ether (200 ml),
and the mixture was refluxed for 2 hours, and then filtered. The
thus obtained solid was purified by silica gel column
chromatography, and evaporated to obtain an orange powder (15.5
g).
[0160] The results of .sup.1H-NMR analysis of the thus-obtained
powder are as follows, and show that the thus obtained orange
powder is a compound [43].
[0161] .sup.1H-NMR (CDCl.sub.3 (d=ppm)): 7.06-8.29 (m, 26H), 8.50
(s, 2H)
[0162] Light absorption characteristics of the compound [43] are as
follows. [0163] Maximum absorption wavelength: 512 nm (thin film:
50 nm) [0164] Full width at half maximum at maximum absorption
wavelength: 103 nm [0165] Absorption coefficient at maximum
absorption wavelength: 2.75.times.10.sup.4 cm.sup.-1
Synthesis Example 3
[0166] Method for Synthesis of Compound [108]
[0167] A mixed solution of 1-bromomethyl-2-dibromomethylnaphthalene
(10.0 g), 1,4-naphthoquinone (5.2 g), sodium iodide (25.5 g) and
dehydrated dimethylformamide (85 ml) was stirred at 70.degree. C.
for 6 hours under a nitrogen flow. The reaction solution was
returned to room temperature, and then filtered. The thus obtained
solid was washed with pure water and methanol, and then filtered.
The thus obtained solid was vacuum-dried to obtain a yellow powder
(4.32 g).
[0168] Next, a mixed solution of 3-phenylbenzofuran (5.9 g) and
dehydrated tetrahydrofuran (50 ml) was stirred at 0.degree. C.
under a nitrogen gas flow. To this mixed solution was added
dropwise n-butyllithium (1.6 M hexane solution (15 ml)), and the
mixture was then stirred at 0.degree. C. for 3 hours. To the
reaction solution was added the yellow powder (3.0 g) for 30
minutes, and the mixture was then stirred at 0.degree. C. for 1
hour. The reaction solution was returned to room temperature, and
further stirred for 1 hour, pure water (100 ml) and toluene (100
ml) were then added, and the mixture was stirred for 30 minutes.
The organic layer was separated, and then dried over magnesium
sulfate, and evaporated to remove the solvent. The thus obtained
solid was recrystallized with toluene to obtain a white powder (5.4
g).
[0169] Next, a mixed solution of the white powder (5.4 g), sodium
hypophosphite monohydrate (8.2 g), potassium iodide (8.5 g) and
acetic acid (80 ml) was refluxed for 2 hours under a nitrogen flow.
To the reaction solution was added pure water (80 ml), and the
mixture was stirred for 30 minutes, and then filtered. To the thus
obtained solid was added cyclopentyl methyl ether (50 ml), and the
mixture was refluxed for 2 hours, and then filtered. The thus
obtained solid was vacuum-dried to obtain a yellow powder (2.7
g).
[0170] The results of .sup.1H-NMR analysis of the thus-obtained
powder are as follows, and show that the thus obtained orange
powder is a compound [108].
[0171] .sup.1H-NMR (CDCl.sub.3 (d=ppm))): 7.08-7.13 (m, 7H),
7.25-7.51 (m, 13H), 7.69-7.75 (m, 3H), 7.89-7.96 (m, 2H), 8.04-8.08
(m, 2H), 8.34-8.35 (m, 2H), 9.19-9.22 (d, 1H, d=7.56Hz)
[0172] Light absorption characteristics of the compound [108] are
as follows. [0173] Maximum absorption wavelength: 492 nm (thin
film: 50 nm) [0174] Full width at half maximum at maximum
absorption wavelength:
[0175] absorption spectrum has no clear peak, and calculation is
impossible. [0176] Absorption coefficient at maximum absorption
wavelength: 3.00.times.10.sup.-4 cm.sup.-1
Synthesis Example 4
[0177] Method for Synthesis of Compound [7]
[0178] To 2,4-diphenylamine (24.5 g) was added 3 N aqueous
hydrochloric acid (300 mL) in an argon atmosphere, and the mixture
was heated to 60.degree. C. in an oil bath, and stirred for 4 hours
to form a hydrochloric acid salt (white suspension liquid). The
white suspension liquid was cooled to 5.degree. C. or lower in a
sodium chloride-ice bath, and an aqueous solution (60 mL)
containing sodium nitrite (8.27 g) was added dropwise for 30
minutes under stirring. Here, the liquid temperature was adjusted
so as not to exceed 10.degree. C. The produced reddish-brown
solution was further stirred at 5.degree. C. for 1 hour to prepare
a diazonium salt solution. An aqueous solution (180 mL) containing
potassium iodide (60 g) was prepared in a beaker, and the prepared
diazonium salt solution was gradually added for 30 minutes under
stirring. The mixture was further stirred for 30 minutes until a
nitrogen gas was no longer generated, and methylene chloride (200
mL) was then added to dissolve the product. A small amount of
sodium hydrogen sulfite was added to decompose iodine generated as
a byproduct, and the organic layer was then separated, washed with
aqueous sodium carbonate and water, and then dried over magnesium
sulfate. The solvent was distilled off under reduced pressure, and
the organic layer was purified by column chromatography to obtain
2,4-diphenyl benzene iodide (29.4 g) (yield: 82.5%).
[0179] 2,4-diphenyl benzene iodide (27.4 g) was dissolved in
dehydrated toluene (180 mL) and dehydrated ether (60 mL) in an
argon atmosphere, and the solution was cooled to -45.degree. C. in
a dry ice-acetone bath. To this was added dropwise a 2.44 M
n-butyllithium-n-hexane solution (31 mL) for 15 minutes, the
temperature was slowly lowered to -10.degree. C., and the mixture
was stirred for 1 hour. To this was added 5, 12-naphthoquinone
(7.75 g) little by little for 30 minutes, the temperature was then
gradually elevated to room temperature, and the mixture was further
stirred for 5 hours. The mixture was cooled to 0.degree. C. with
iced water, and methanol (60 mL) was added dropwise. The produced
powder was collected by filtration, washed with cold methanol
several times, and vacuum-dried to obtain a white powder. Toluene
(200 mL) was added, and the mixture was heated and suspended for 1
hour, and cooled to room temperature. The mixture was filtered,
washed with cold toluene, and vacuum-dried to obtain a white powder
of a diol (15.1 g) (yield: 69.8%).
[0180] The following reaction was carried out while a flask
provided with an argon blowing tube was shielded against light with
an aluminum foil. To the diol (14.42 g) was added degassed
tetrahydrofuran (THF) (450 mL), and the diol was dissolved by
stirring the mixture while blowing argon. Therefore, the solution
was heated to 40.degree. C. in an oil bath. To this was added
dropwise a concentrated hydrochloric acid aqueous solution (150 mL)
containing tin dichlorate dihydrate (45.1 g) for 90 minutes.
Thereafter, the temperature of the oil bath was elevated to
70.degree. C., and the mixture was stirred under reflux for 2
hours, and cooled to room temperature. A 2 L beaker was shielded
against light, distilled water (1 L) was added therein, and
degassing was performed by feeding an argon flow. The reaction
liquid was added therein, and the mixture was stirred for 30
minutes. The precipitated yellow powder was collected by
filtration, and added in distilled water (1 L) again, and the
mixture was stirred and washed. The mixture was filtered,
sufficiently washed with methanol, and then vacuum-dried. This was
heated and suspended in acetone (250 mL) degassed by blowing argon,
and the suspension was filtered and vacuum-dried to obtain an
orange-yellow powder of a desired compound [7] (12.70 g) (yield:
92.7%).
[0181] Optical characteristics of the compound [7] are as follows.
[0182] Maximum absorption wavelength: 506 nm (thin film: 50 nm)
[0183] Full width at half maximum at maximum absorption wavelength:
23 nm [0184] Absorption coefficient at maximum absorption
wavelength: 4.65.times.10.sup.4 cm
Example 1
[0185] A photoelectric conversion element using the compound [10]
was produced in the following manner. A glass substrate
(manufactured by Asahi Glass Co., Ltd., 15 .OMEGA./.quadrature.,
electron beam vapor-deposited product) including an ITO transparent
conductive film having a film thickness of 150 nm deposited thereon
was cut into pieces of 30.times.40 mm in size, followed by etching.
The substrate thus obtained was subjected to ultrasonic cleaning
for 15 minutes each, using acetone and "SEMICOCLEAN (registered
trademark) 56" (manufactured by Furuuchi Chemical Corporation), and
then washed with ultra-pure water. Subsequently, the substrate was
subjected to ultrasonic cleaning with isopropyl alcohol for 15
minutes, then immersed in hot methanol for 15 minutes, and dried.
Immediately before the production of a photoelectric conversion
element, this substrate was subjected to a UV ozone treatment for 1
hour. After placing in a vacuum vapor deposition device, the inside
of the device was evacuated until the degree of vacuum became
5.times.10.sup.-5 Pa or less. Molybdenum oxide was vapor-deposited
as an electron blocking layer in a film thickness of 30 nm by a
resistance heating method. Next, as a photoelectric conversion
layer, the compound [10] being a p-type semiconductor material and
the compound A-1 being a n-type semiconductor material were
co-deposited in a film thickness of 70 nm at a vapor deposition
rate ratio of 1:3. Next, aluminum was vapor-deposited as a cathode
in a film thickness of 60 nm to produce a photoelectric conversion
element of 2.times.2 mm square. The film thickness as used herein
is an indicated value of a crystal oscillation type thickness
monitor.
[0186] For production of a substrate for absorption spectrum
measurement, a quartz substrate was placed in the same chamber
concurrently with vapor deposition of the photoelectric conversion
layer, so that a 70 nm-thick thin film was formed on the quartz
substrate.
[0187] The absorption spectrum of vapor-deposited film on the
quartz substrate at 400 nm to 700 nm was measured using an
ultraviolet/visible spectrophotometer. Light absorption
characteristics are as follows. [0188] Maximum absorption
wavelength: 525 nm [0189] Full width at half maximum at maximum
absorption wavelength: 143 nm [0190] Absorption coefficient at
maximum absorption wavelength: 9.88.times.10 .sup.4 cm.sup.-1
[0191] Spectral sensitivity characteristics in application of a
bias voltage (-3 V) to the photoelectric conversion element are as
follows. [0192] Maximum sensitivity wavelength: 540 nm [0193]
External quantum efficiency at maximum sensitivity wavelength:
50%
[0194] In the present invention, photoelectric conversion
efficiency is evaluated by external quantum efficiency at the
maximum sensitivity wavelength.
Examples 2 to 9
[0195] Except that the types of a p-type semiconductor material and
a n-type semiconductor material, and the vapor deposition rate
ratio were set as shown in Table 1, the same procedure as in
Example 1 was carried out to produce a photoelectric conversion
element. Light absorption characteristics and spectral sensitivity
characteristics are shown in Table 1.
TABLE-US-00001 TABLE 1 External quantum efficiency at Absorption
maximum Full coefficient sensitivity p-type n-type Vapor Maximum
width at maximum Maximum wavelength (%) Electron semi- semi-
deposition absorption at half absorption sensitivity Voltage
Voltage blocking conductor conductor rate ratio wavelength maximum
wavelength wavelength applied: applied: layer material material
(p-type:n-type) (nm) (nm) (cm.sup.-1) (nm) none -3 V Example 1
MoO.sub.3 Compound A-1 1:3 525 143 9.88 .times. 10.sup.4 540 18 50
[10] Example 2 MoO.sub.3 Compound A-1 1:1 525 140 8.90 .times.
10.sup.4 530 14 39 [10] Example 3 MoO.sub.3 Compound A-1 3:1 505
139 3.09 .times. 10.sup.4 510 10 34 [10] Example 4 MoO.sub.3
Compound A-1 1:3 526 149 9.34 .times. 10.sup.4 540 10 43 [43]
Example 5 MoO.sub.3 Compound A-1 1:1 525 144 7.44 .times. 10.sup.4
520 3 32 [43] Example 6 MoO.sub.3 Compound A-1 3:1 505 139 3.09
.times. 10.sup.4 500 1 11 [43] Example 7 MoO.sub.3 Compound A-1 1:3
524 137 9.11 .times. 10.sup.4 530 3 35 [108] Example 8 MoO.sub.3
Compound A-1 1:1 524 143 9.88 .times. 10.sup.4 540 5 36 [108]
Example 9 MoO.sub.3 Compound A-1 3:1 500 148 3.50 .times. 10.sup.4
490 1 12 [108]
Examples 10 to 30
[0196] Except that as an electron blocking layer, PEDOT/PSS
(Clevios.TM. P VP A14083) was applied in a film thickness of 30 nm
instead of vapor-depositing molybdenum oxide in a film thickness of
30 nm, and the types of a p-type semiconductor material and a
n-type semiconductor material, and the vapor deposition rate ratio
were set as shown in Table 2, the same procedure as in Example 1
was carried out to produce a photoelectric conversion element.
Light absorption characteristics and spectral sensitivity
characteristics are shown in Table 2.
##STR00051##
TABLE-US-00002 TABLE 2 External quantum efficiency at Absorption
maximum Full coefficient sensitivity p-type n-type Vapor Maximum
width at maximum Maximum wavelength (%) Electron semi- semi-
deposition absorption at half absorption sensitivity Voltage
Voltage blocking conductor conductor rate ratio wavelength maximum
wavelength wavelength applied: applied: layer material material
(p-type:n-type) (nm) (nm) (cm.sup.-1) (nm) none -3 V Example 10
PEDOT: PSS Compound A-1 1:3 525 143 9.88 .times. 10.sup.4 510 18 53
[10] Example 11 PEDOT: PSS Compound A-1 1:1 525 140 8.90 .times.
10.sup.4 530 27 64 [10] Example 12 PEDOT: PSS Compound A-1 3:1 505
139 3.09 .times. 10.sup.4 540 14 47 [10] Example 13 PEDOT: PSS
Compound A-1 1:3 526 149 9.34 .times. 10.sup.4 540 4 25 [43]
Example 14 PEDOT: PSS Compound A-1 1:1 525 144 7.44 .times.
10.sup.4 520 5 34 [43] Example 15 PEDOT: PSS Compound A-1 3:1 505
139 3.09 .times. 10.sup.4 510 3 25 [43] Example 16 PEDOT: PSS
Compound A-1 1:3 524 137 9.11 .times. 10.sup.4 530 5 36 [108]
Example 17 PEDOT: PSS Compound A-1 1:1 524 143 9.88 .times.
10.sup.4 540 7 37 [108] Example 18 PEDOT: PSS Compound A-1 3:1 500
148 3.50 .times. 10.sup.4 490 1 14 [108] Example 19 PEDOT: PSS
Compound A-1 1:1 522 140 9.64 .times. 10.sup.4 520 16 52 [7]
Example 20 PEDOT: PSS Compound A-2 1:3 477 90 5.66 .times. 10.sup.4
480 6 38 [10] Example 21 PEDOT: PSS Compound A-2 1:1 479 90 4.37
.times. 10.sup.4 470 7 36 [10] Example 22 PEDOT: PSS Compound A-2
3:1 473 97 2.15 .times. 10.sup.4 470 2 20 [10] Example 23 PEDOT:
PSS Compound A-2 1:3 481 93 4.68 .times. 10.sup.4 490 1 14 [43]
Example 24 PEDOT: PSS Compound A-2 1:1 481 93 4.56 .times. 10.sup.4
480 1 15 [43] Example 25 PEDOT: PSS Compound A-3 1:3 502 110 5.99
.times. 10.sup.4 480 4 47 [10] Example 26 PEDOT: PSS Compound A-3
1:1 503 77 4.41 .times. 10.sup.4 480 11 43 [10] Example 27 PEDOT:
PSS Compound A-3 3:1 503 23 5.16 .times. 10.sup.4 470 3 17 [10]
Example 28 PEDOT: PSS Compound A-3 1:3 508 100 5.94 .times.
10.sup.4 490 4 38 [43] Example 29 PEDOT: PSS Compound A-3 1:1 501
106 4.78 .times. 10.sup.4 490 6 38 [43] Example 30 PEDOT: PSS
Compound A-3 3:1 499 110 3.64 .times. 10.sup.4 500 1 10 [43]
Comparative Examples 1 to 7
[0197] Except that only one of a n-type semiconductor material and
a p-type semiconductor material was used in a photoelectric
conversion layer, the same procedure as in Example 1 was carried
out to produce a photoelectric conversion element. Light absorption
characteristics and spectral sensitivity characteristics are shown
in Table 3.
##STR00052##
TABLE-US-00003 TABLE 3 External quantum efficiency at Absorption
maximum Full coefficient sensitivity p-type n-type Vapor Maximum
width at maximum Maximum wavelength (%) Electron semi- semi-
deposition absorption at half absorption sensitivity Voltage
Voltage blocking conductor conductor rate ratio wavelength maximum
wavelength wavelength applied: applied: layer material material
(p-type:n-type) (nm) (nm) (cm.sup.-1) (nm) none -3 V Comparative
MoO.sub.3 Compound 504 23 4.72 .times. 10.sup.4 0 0 Example 1 [10]
Comparative MoO.sub.3 Compound 512 103 2.75 .times. 10.sup.4 0 0
Example 2 [43] Comparative MoO.sub.3 Compound 492 None 3.00 .times.
10.sup.4 0 0 Example 3 [108] Comparative MoO.sub.3 A-1 533 163 1.16
.times. 10.sup.5 570 0 4 Example 4 Comparative MoO.sub.3 A-2 489
105 6.51 .times. 10.sup.4 0 0 Example 5 Comparative MoO.sub.3 A-3
500 113 8.65 .times. 10.sup.4 0 0 Example 6 Comparative MoO.sub.3
A-4 547 70 2.34 .times. 10.sup.4 0 0 Example 7 Comparative
MoO.sub.3 Compound A-4 1:1 516 83 2.97 .times. 10.sup.4 520 0 1
Example 8 [10] Comparative MoO.sub.3 Compound A-4 1:1 504 45 2.90
.times. 10.sup.4 500 0 1 Example 9 [43] Comparative MoO.sub.3
Compound A-4 1:1 496 57 2.69 .times. 10.sup.4 500 0 1 Example 10
[108]
Comparative Example 8
[0198] Except that a compound A-4 was used as a n-type
semiconductor material, the same procedure as in Example 1 was
carried out to produce a photoelectric conversion element. Light
absorption characteristics and spectral sensitivity characteristics
are shown in Table 3.
Comparative Examples 9 and 10
[0199] Except that as a p-type semiconductor material, one as shown
in Table 3 was used, the same procedure as in Comparative Example 7
was carried out to produce a photoelectric conversion element.
Light absorption characteristics and spectral sensitivity
characteristics are shown in Table 3.
INDUSTRIAL APPLICABILITY
[0200] The photoelectric conversion element of the present
invention can be applied in the fields of image sensors and solar
cells. Specifically, the photoelectric conversion element can be
employed in the fields of image elements mounted in mobile phones,
smartphones, tablet PCs, digital still cameras, and the like; and
sensing devices such as photovoltaic power generating apparatuses
and visible light sensors.
DESCRIPTION OF REFERENCE SIGNS
[0201] 10: First electrode
[0202] 11: Organic layer
[0203] 13: Electron blocking layer
[0204] 15: Photoelectric conversion layer
[0205] 17: Hole blocking layer
[0206] 20: Second electrode
[0207] 31: Photoelectric conversion element for detecting red
light
[0208] 32: Photoelectric conversion element for detecting green
light
[0209] 33: Photoelectric conversion element for detecting blue
light
[0210] 34: Incident light
* * * * *